Donald Trump is not considering sacking the special counsel investigating Russian election interference, a top White House lawyer said, after a cascade of tweets revived speculation the US president may be preparing to get rid of the veteran prosecutor.

The statement from White House lawyer Ty Cobb came after top congressional Republicans warned of repercussions if Mr Trump removed special counsel Robert Mueller, who is looking into contacts between the president’s 2016 campaign and Russian meddling in the election.

In a series of weekend tweets, Mr Trump jabbed directly at Mr Mueller by name for the first time. The president challenged the investigation’s existence and suggested political bias on the part of Mr Mueller’s investigators.

Mr Trump has long been frustrated by the lengthy and intensifying probe, and insists his campaign did not collude with Russia to influence the election in his favour.

“The Mueller probe should never have been started in that there was no collusion and there was no crime,” he said in a late Saturday tweet he ended with: “WITCH HUNT!”

Likely contributing to Mr Trump’s sense of frustration, The New York Times reported last week that Mr Mueller had subpoenaed the Trump Organisation for Russia-related documents. Mr Trump had said Mr Mueller would cross a red line with such a step.

“Why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans?” Mr Trump tweeted on Sunday.

Some of Mr Mueller’s investigators have contributed to Democratic political candidates, but Justice Department policy and federal service law bar discrimination in the hiring of career positions on the basis of political affiliation. Mr Mueller is a Republican.

The tweets revived talk that Mr Trump may, in an attempt to end the investigation, move to have Mr Mueller sacked. Mr Cobb sought to dampen down the speculation.

“In response to media speculation and related questions being posed to the Administration, the White House yet again confirms that the president is not considering or discussing the firing of the special counsel, Robert Mueller,” he said.

On Sunday, members of US congress, including some top Republicans, warned Mr Trump not to even think about removing Mr Mueller.

“If he tried to do that, that would be the beginning of the end of his presidency,” said senator Lindsey Graham, a Trump ally.